<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
    
    //es6 中的 箭头函数

    let hello = () => {
        console.log("hello es")
    }

    hello()

    function add(x = 0, y = 0) {

        return x + y
    }

    console.log(add(1,2))
    console.log(add(1))

    let del =  a => console.log(a)

    let a = 10
    del(a)


    </script>
</body>
</html>